Pressure-actuated stepping switch



Feb 24, 1959 oIJ. SAHOLT 2,875,292 PRESSURE-ACTUATED STEPPING SWITCHFiled July 18, 1958 s Sheets-Sheet 2 INVENTOR ORVILLE J. SAHOLT ATTOR NEYS.

Feb. 1959 o. J. SAHOLT 2,875,292

PRESSURE-ACTUATED STEPPING SWITCH Filed July 18, 1958 3 Sheets-Sheet 3INVENTOR. QRVILLE J. SAHOLT in/19m ATTORNEYS.

United States Patent PRESSURE-ACTUATED STEPPING SWITCH Orville J.Saholt, China Lake, Calif., assignor to the United States of America asrepresented by the Secretary of the Navy The invention herein describedmay be manufactured and used by or for the Government of the UnitedStates of America for governmental purposes without the payment of anyroyalties thereon or therefor.

The present invention relates to electrical switches and particularly toa gas pressure actuated stepping switch for closing electrical circuitsin a specific sequence.

The switch of the present invention is a wafer-type switch mountedconcentrically around a gas-operated piston such that a cam surface onthe piston controls the advancement of the switch. It basically c0nsistsof a piston with a cam surface, a torsionally Spring loaded contact discand a fixed contact assembly. This switch has a particular use inclosing igniter circuits of a multiple grain rocket motor in a specificsequence, preventing the ignition of any grain segment until the grainsegment that precedes it has been expended. The gas pressure developedby each grain segment is used to operate the switch by moving the pistontherein. Gas pressure moves the piston with the cam surface and thuspermits the rotary spring-loaded contact to move half the distancebetween fixed contacts. When the gas pressure is reduced, as the grainis expended, the rotary contact moves to the next fixed contact closingthe next circuit, thus firing the next gram.

It is an object of the present invention to provide a pressure actuatedstepping switch for sequentially closing electrical circuits.

Another object of the present invention is to provide a gas operatedstepping switch.

A further object of the invention is to provide a new stepping switchhaving a gas operated piston with a cam surface thereon for controllingthe advancement of the switch.

Other objects and many of the attendant advantages of this inventionwill become readily appreciated as the same becomes better understood byreference to the following detailed description when considered inconnection with the accompanying drawings wherein:

Fig. l is a side cross-sectional view of the gas pressure operatedstepping switch;

Fig. 2 is a side view of the piston cylinder showing the cam surface;

Fig. 3 is a cross-sectional view of the piston cylinder taken along theline 33 of Fig. 2;

Fig. 4 shows a plan view of the contact disc;

Fig. 5 is a cross-sectional side view of the contact disc taken alongthe lines 55 of Fig. 4;

Fig. 6 is a plan view of the switch contact plate showing the terminalsof the switch surface;

Fig. 7 shows the opposite side of the switch contact plate assemblyillustrated in Fig. 6;

Fig. 8 is a cutaway section, taken along line 8-8 of Fig. 7, showingelectrical lead wire connection to the contact surface of the switchcontact plate.

Referring now to the drawings like numerals refer to like parts in eachofthe figures.

The switch assembly 10, illustrated in Fig. 1, comprises a housing 12entirely open at end 13 and having a passage 14 at the other end throughwhich electrical lead wires pass. A base 16 completely encloses theentire open end 13 of housing 12. The base has an upwardly extendingflange 17 about the periphery thereof which is of the size to fit withinand completely close open end 13 of the housing; and a shaft 18 thatextends upwardly from the center of the base. Between the peripheralflange 17 and central shaft 18 is another flange 20 which extendsupwardly from the base slightly less than the length of peripheralflange 18. Central shaft 18 has a passage 22 therethrough for thepassage of gas to operate the switch; the top end'of shaft 18 is beveledinwardly toward passage 22 forming a small cup-shaped chamber 23. Acircumferential groove 25 extends about shaft 18 at a small top thereof;an O-ring 26 fits within groove 25.

In Figures 1, 2 and 3 is illustrated a cylindrical piston 30 having ahollow portion 32 which fits over shaft 18; piston 30 is operable toride up and down on shaft 18. Hollow portion 32 of the piston is ofsubstantially the same size as shaft 18 with just enough clearance toallow up and down movement on the shaft. The upper end of piston 30 hasa chamfer 34 about its periphery, and a flange 35 near the top of thepiston which extends about the circumference thereof. Beneath flange 35,there is a cam surface on the outer cylindrical surface of the piston.This cam surface consists of a plurality of cam teeth 37 and 38 whichextend from the cylindrical surface of the piston to the outer diameterof flange 35. Cam teeth 37 and 38 are spaced alternately and equidistantabout the cylindrical surface of the piston. Cam teeth 37 extend fromflange 35 to slightly more than half way to the bottom of the piston,and cam teeth 38 extend from the bottom of the piston to slightly morethan half way to flange 35; thus cam teeth 37 and 38 overlap slightly upand down about the circumference of the piston, the space between thecam teeth forming a somewhat zig zag path about the circumference of thepiston cylinder, as can be seen from Fig. 2. Two small passages 40extend through the walls of the piston cylinder from top to bottom;similar and related passages 41 pass through the top of housing 12, andpassages 42 pass through base 16. Pins 44 fit within passages 40, 41 and42 for guiding piston 30 as it rides up or down and preventing thepiston from rotating about shaft 18. A bias spring 46, which fits aboutthe top end of the piston against flange 35 and extends to the top ofthe housing, tends to force the piston downward v on the shaft.

A contact disc 50 (Figures 1, 4 and 5), having an outer diameter whichis nearly the same as the outer diameter of flange 17 on base 16, ismovably supported for rotation within housing 12 between the top offlange'17 and step 51 along the inside wall of the housing. Contact disc50 has a central opening 52 which is slightly larger than the outerdiameter of flange 35 on the piston, and has a plurality of pins 54fixedly spaced equidistant about the circumference of central opening 52and extending radially from the outer periphery of disc 50 into opening52 for a distance almost equal to the depth of cam teeth 37 and 38. Thecontact disc 50 is preferably made of a nonconductive material whereaspins 54 are preferably made of metal. A pin 56 extends through thecontact disc and is connected to one end of a clock spring 58 housed inbase 16 between flanges 17 and 20. The other end of clock spring 58 isfastened to the base, and when it is wound-up will tend to cause thecontact disc to rotate. Contact disc 50, movably mounted in the housing,fits about piston 30 so that it is always just below flange 35 on thepiston, and pins 54 bear against cam teeth 37 or 38 due to the torsionalforce of the clock spring. This contact disc carries a depressablespring type slide contact 60 mounted on its surface opposite to thesurface fac Patented Feb. 24, 1959 distance below theing-, tlreclochspring. Siidg contact 60 contacts the surcsq the w tshy atast,platsfifii r lssins nd wning electrical circuits in sequence,

Switch contact plate 65 is; best illustrated in Fig. 6,

nd; cgn is s, o a} di c o n ativ a e al a g central opening-660i?greater diameter than piston flange 35,apd having}an electricallyconductive pattern thereon whi hrnake-up the common terminal 67 and aplurality onsequence terminals; 68. The switch surfaces, terminals #29168,- may e ons ruc by p n rcui techniques rather: than by; theconventional type construction frwats r y w qhe rp p in o h Operatingswitch whichjsless expensive to manufacture and allowing; azrnore.compact; assembly. Contact disc'50 with its slide contact together withswitch contact plate formand; operate like a wafer-type switch.

lnfiigpres 1, and 7 is illustrated the contact plate assembly. Acircumferential flange of insulative material, haYi-ng-anouter diameterthe same asthat of switch contact plate; 65, is mounted on the contact;plate on the opposite;side toierminals 67 and68. A spacer flange 72ofr'insnlating; material havingan inner diameter the samecentral'opening 66 and slightly higher than flange 70, issalsomounted-onthe side of the contact plate opposite torterminals 6.7 and 68. Holesare drilled-through switch contacts plate 65 and terminals and ends ofelectrical leadsr arepassed-therethrough from the opposite side,asishowninFigures7 and'8. The lead ends 76 are soldared tothe terminals,then the terminal surfaces are ground and polished, after a pottingcompound 78 is poured-:between flanges 70 and 72 to hold wires '75firmly in place, so that terminals 67 and have a smooth surface The.entire contact assembly fits snugly within the upperportion of'housing12-and electrical lead wires 75 pass-out through opening 14 therein. Theupper end of spacer flange 72 rests against the inner top surface ofhousing-12 correctly positioning the contact plate assembly within thehousing so that slide contact 60 will properly-slide over terminals 67and 68 on the contact plate making good electrical contact. Pistonspring 46 and the upperend of piston 30 are positioned and free to movein the space within circumferential spacer flange 72.

The-stepping switch operates as follows:

Gas pressure, from an ignited gas producing grain or othersource, isused to actuate piston 30 by forcing it upwards until contact disc pins54 no longer bear against piston cam teeth 37 andcontact disc 50 isrotated by torsionally loaded clock spring 58 for a half positionopening electrical contacts and. bringing pins 54 to bear against camteeth 38. The electrical contacts remain open as long as the gaspressure is maintained to keep piston 30 forced upward. O-ring 26 on theshaft tends to preventgas from leaking between the piston and shaft intothe inside of the housing. Whenthegas pressure drops cis t y spr ng 4 rv s, e pi t nba ko to its g iel PSit Q 1.( 9Wn n isre i f l nof ser h aa a nst mtcet 38, u llo the contact dise torotateanother half position,whichcloses, theswitch contacts in a position adjacent to the.

starting position, to where pins 54' bear against cam teeth 37preventing further rotation of the contact disc until thepi ston is actuated again, The sequence repeats each time gas pressure actua tes thepiston until a complete rotation of the contact disc is completed.

Instead of using a clock spring for torsionally loading the contact discthe cam teeth may bede signed so as to drive. the contact disc a halfposition on thetgas pressure stroke and then drive it the remaining halfposition on the returnv stroke.

Qbviously many modifications and variations of the present invention arepossible in the light'of the above teachings-.- It is therefore tobeunderstood that within theseopeofrtheappended claims the invention maybe practiced-,- otherwise than as specifically described.

What is claimed is:

A sasrrsssnreas uatest terpias. witch amusin a housing member completelyopen at one end, a base member which encloses the: open end of saidhousing member, a central shaft which extends upwards from said baseinto said housing member, a hollow cylindrical piston on said shaftandhaving a cam surface on the outer cylindrical surface thereof, saidpiston being operable to ride up and down upon said shaft, a bias springfor normally biasing said piston downward on said shaft, a passage. insaid shaft'and baseflextending from an external source of gas pressureto the upper end of said shaft, said piston operable to'be actuated bybeing forced upward under gas pressure, a torsionally spring loadedcontact disc having a central aperture therein through which said pistonextends, said disc having means thereon for riding on said piston camsurface, a fixed contact assembly within said housing having switchterminals thereon and being normally contacted by said contact disc,said cam snrface being operable to allow-said torsionally loaded springcontact disc; to rotate, ahalf position opening contact between-a pairof switch terminals when said pistonis raised by gas pressure and againto rotate another half position when gas pressure drops allowing saidpiston to be returned to its. originalv position thereby closing switchterminals on thercontact assembly in a position adjacent to the-startingposition, the sequence repeating each time the piston is'pressurizeduntil a complete rotation of the contact disc is made.

2. A- gas-pressure actuated stepping switch comprising a housing memberopen at one end, a base member for completely closing the open end ofsaid housing, a central shaft which extends upwards from said basemember intosaid housing and a hollow pistonwhich is operable to ride upand down upon said shaft, meansfor normally biasing said piston downwardon saidshaft, acam means on said piston, a passage extending from thetop of said central shaft to an external source of gas pressure, saidpiston-operable to be actuated by beingforced upward under gas pressure,a contact disc in said housing, said contact disc having means thereonfor riding on said piston cam means, a fixed contact assembly in saidhousing having a plurality of switch terminals thereon normallycontacted by said contact disc, said contact disc normally completing anelectrical circuit between two of said switch terminals, said cam meansbeing operable to rotate said contact disc a half position and open theelectrical contact betweenthe two of said'switch terminals when saidpiston is raised by gas pressure and again to rotate the c'ontactdiscanother half position when gas pressure drops allowing said piston toreturn to its orig inal position thereby closing electrical contactsbetween switch terminals on the contact assembly in a positionadjacentto the starting position, the sequence of opening and closingelectrical contact between adjacent switch terminals repeating each timethepiston is pressure actuated until a complete rotation ofthecontact'dise is made.

3. A gas-pressure actuated steppingswitch comprising a housing membercompletely open atone end and having a small aperture at the oppositeend throughrwhich electrical lead, wires pass, a base; member whichcompletely encloses the open endof said housing member, a shaft whichextends approximately half-way upward from the center of said basemember into said housing member, a hollow cylindrical piston on saidshaft and having cam means thereon, saidpiston being operable to ride upand down upon said shaft, abias springpositioned between the top of saidpiston and theinside top of said housing for normally biasing saidpiston downward on said shaft, means preventing rotation of said pistonabout said shaft, a passage in said shaft extending froma source of gaspressure external of said housingmember through said base member'to theupper. end of said shaft, said piston operable to be actuated by beingforced upward 5 under gas pressure, a contact disc in said housingcarrying a slide contact thereon and having a central aperture thereinthrough which said piston extends, said disc having means thereon forriding on said cam means, means normally tending to rotate said contactdisc, a fixed contact assembly in said housing having switch terminalsthereon and being normally contacted by said slide contact, said cammeans permitting said contact disc to rotate and move the slide contacta half position opening electrical contact between switch terminals onsaid fixed contact assembly when said piston is raised by gas pressureand again to rotate moving the slide contact another half position whengas pressure drops allowing said piston to be returned to its originalposition thereby closing electrical contact between switch terminals onthe contact assembly in a position adjacent to the starting position,the sequence of opening and closing electrical contact between adjacentswitch terminals repeating each time the piston is pressurized until acomplete rotation of the contact disc is made.

References Cited in the file of this patent UNITED STATES PATENTS1,766,600 Caruso June 24, 1930 2,828,636 Hall Apr. 1, 1958 2,851,646Williamson et al. Sept. 9, 1958

